take -containers -bytestring

take n, applied to a list xs, returns the prefix of xs of length n, or xs itself if n > length xs:
> take 5 "Hello World!" == "Hello"
> take 3 [1,2,3,4,5] == [1,2,3]
> take 3 [1,2] == [1,2]
> take 3 [] == []
> take (-1) [1,2] == []
> take 0 [1,2] == []
It is an instance of the more general Data.List.genericTake, in which n may be of any integral type.

Return the contents of the MVar. If the MVar is currently empty, takeMVar will wait until it is full. After a takeMVar, the MVar is left empty.
There are two further important properties of takeMVar:
* takeMVar is single-wakeup. That is, if there are multiple threads blocked in takeMVar, and the MVar becomes full, only one thread will be woken up. The runtime guarantees that the woken thread completes its takeMVar operation.
* When multiple threads are blocked on an MVar, they are woken up in FIFO order. This is useful for providing fairness properties of abstractions built using MVars.

O(1) Return the prefix of the Text of n Word16 units in length.
If n would cause the Text to end inside a surrogate pair, the end of the prefix will be advanced by one additional Word16 unit to maintain its validity.